My 340 getting 6 mpg
So I'll chime in on carb choice. The carb you have has mechanical secondaries. When you floor it the secondaries are wide open no matter what, plus a double shot from the accelerator pumps (they did that to cover the massive sudden vacuum drop in the carb). You could use a Holley with vacuum secondaries, or an Edelbrock AFB or AVS2. All those carbs have secondaries that are controlled by the demand for air/fuel by the engine. With them you can guess high on the size of the carb and the secondaries might not be all the way open until the top end rpms. I'd try an 800 AVS2.
If I can get 15 mpg out of my 340 with 2 Eddie AFB 500s, you can do better than you are doing! By the way I absolutely love your car!
So I'll chime in on carb choice. The carb you have has mechanical secondaries. When you floor it the secondaries are wide open no matter what, plus a double shot from the accelerator pumps (they did that to cover the massive sudden vacuum drop in the carb). You could use a Holley with vacuum secondaries, or an Edelbrock AFB or AVS2. All those carbs have secondaries that are controlled by the demand for air/fuel by the engine. With them you can guess high on the size of the carb and the secondaries might not be all the way open until the top end rpms. I'd try an 800 AVS2.
If I can get 15 mpg out of my 340 with 2 Eddie AFB 500s, you can do better than you are doing! By the way I absolutely love your car!